The Profinet standard, among others, which supports the controlling of field devices such as sensors and actuators by a higher-level control device, is used in automation technology.
One version of the Profinet standard is Profinet-IO, which is based on Ethernet technology. Profinet-IO was developed inside the Profibus user organization and standardized in IEC61158/IEC61784. Profinet-IO supports a so-called provider-consumer model, in which data is transmitted cyclically in real time from a data source, which is called a provider, to a data sink, which is called a consumer. Such providers and consumers are implemented both in an I/O control device and in I/O field devices. The cyclical data exchange between an I/O control device and a decentralized I/O field device takes place by way of a communication relationship (CR), which is set up between a provider and a consumer. A communication relationship of the control device to a field device is referred to as an output CR, while the communication relationship of a field device to the control device is referred to as an input CR.